Control device for a circuit breaker

ABSTRACT

Described herein is a control device for a circuit breaker, which is so arranged that an electric power is supplied to a high potential side through an insulating transformer thereby to charge a capacitor, said capacitor being discharged by an operating signal thereby to start a switching operation at a great rate; in which a current limit device is provided on the ground side of the said insulating transformer as a result of which the insulating transformer can be made smaller, a switching operation can be achieved even in the re-charging period of the capacitor, and a recharging time of the capacitor is made shorter, and furthermore a pressure or stress wave propagating in an insulation bar is utilized so as to accurately transfer an operating signal issued from the ground side to a discharge gap placed on the high potential side without time delay.

United States Patent Nitta et al.

CONTROL DEVICE FOR A CIRCUIT BREAKER Inventors: Yoshio Nitta; NobuakiKiyokuni;

Kikuo Kawasaki, all of Kawasaki, Japan [73] Assignee: Fuji Denki SeizoKabushiki Kaisha,

Kawasaki-shi, Kanagawa-ken, Japan [22] Filed: Nov. 15, 1971 [21] Appl.No.: 198,795

[52] US. Cl 307/143, 317/151 [51] Int. Cl. .1 1101b 47/00 [58] Field ofSearch 307/143, 109; 317/31, 33 SC, 27 R, 151; 320/1 [56] ReferencesCited UNITED STATES PATENTS 3,213,321 10/1965 Dalziel 317/151 X3,312,875 4/1967 Mayer 317/151 X HIGH POTENTIAL GROUND SIDE SIDE PrimaryExaminer-Robert K. Schaefer Assistant Examiner-William J. SmithAttorney-Holman & Stern [57] ABSTRACT Described herein is a controldevice for a circuit breaker, which is so arranged that an electricpower is supplied to a high potential side through an insulatingtransformer thereby to charge a capacitor, said capacitor beingdischarged by an operating signal thereby to start a switching operationat a great rate; in which a current limit device is provided on theground side of the said insulating transformer as a result of which theinsulating transformer can be made smaller, a switching operation can beachieved even in the re-charging period of the capacitor, and arecharging time of the capacitor is made shorter, and furthermore apressure or stress wave propagating in an insulation bar is utilized soas to accurately transfer an operating signal issued from the groundside to a discharge gap placed on the high potential side without timedelay.

7 Claims, 7 Drawing Figures 1 CONTROL DEVICE FOR A CIRCUIT BREAKERBACKGROUND OFTHE INVENTION The present invention relates to a controldevice for a circuit breaker used in power transmission system.

As well known, troubles with respect to a transmission line of anextra-high voltage system results in damages much more serious thanthose involved in troubles of a lower-voltage system. Therefore, a planshould be made so that causes for those troubles be removed as soon aspossible thereby to quickly restore the power transmission ability.Accordingly, required for such system mentioned above is a circuitbreaker that can accomplish a high speed breaking operation and has thefunction of a high speed reclosing operation.

For this purpose, a device has been disclosed, in which electro-staticenergy stored in a capacitor is used for driving a movable contact of ahigh-voltage circuit breaker. It is also well known to supply chargingenergy to a capacitor on the high potential side through a cascadeconnected insulating transformer installed between the ground side andhigh potential side. Furthermore, it is publicly known a lightpropagating through an insulation bar is employed as an operating signalissued from the ground side.

In addition to the above, a circuit breaker meeting the above-mentionedrequirement has been developed by the applicant and is now used in anactually loaded system.

' The technical arrangement of this circuit breaker is described indetail in the specification of U.S. Pat. No. 3,315,056. The principle ofthe breaking operation revealed in the patent resides in that anelectromagnetic repulsion force is produced between a movable contactand a driving coil, provided oppositely to the stationary contact, bydischarging electrostatic energy of a operating capacitor into thedriving coil, the thus produced repulsion force being utilized so as toinstantaneously drive the movable contact apart from a stationarycontact. Therefore, if this driving principle is applied to a shortcircuiter or a closing device, a reasonable closing operation can beobtained in the same way as-breaking operation in the circuit breaker.

However, in general, the specification of the operating capacitoradapted to instantaneously drive the movable contact is required tobelarge in capacity and high in voltage. Therefore, in the case where thecapacitor of this type is installed in a high potential casing withapplied a high voltage, disadvanteously it may take a long time tore-charge the capacitor after it having been discharged. In case of suchoperating capacitor employed for the extra-high voltage circuit breakermentioned previously, the capacitor should be recharged so that itsvoltage quickly reaches a predetermined voltage within a short time onthe basis of the operational requirement such as high speed reclosing.Therefore, an operating power source device for this purpose should be acharging device having a large capacity, for instance, several kVA.However, such device involves disadvantages that it is considerably highin cost and heavy in weight. In addition, how to suppress or control alarge rush current in the recharging operation and how to quicklyachieve the recharging operation are the problems given to the device ofthis type.

SUMMARY OF THE INVENTION A primary object of the present inventionresides in the fact that a current limit device is provided on theground side in order to suppress or control a charging rush currentflowing to a capacitor of a circuit breaker, and said control deviceplaced on a high potential side is made operative.

Another object of the present invention resides in the fact that acharging current for an operating capacitor of control device isobtained by means of a current transformer and a re-closing operationcan be successfully accomplished with no trouble even in a period of are-charging operation.

A further object of the present invention is to make a charging voltageof an operating capacitor higher than a predetermined value by atap-changing operation only when it is charged, in order to make shorterthe re-charging time of the operating capacitor.

A still further object resides in that a pressure wave signal through aninsulation bar is utilized in order to accurately transfer an operatingsignal issued from the ground side to a discharge gap placed on a highpotential side without time delay.

A particular object of the present invention is to improve thedischarging characteristic of the spark gap thereby to achieve abreaking operation without serious time delay.

A more particular object of the present invention resides in that achange-over switch used for the reclosing operation is constructed as aflip-flop valve thereby to obtain an accurate change-over operation foroperating capacitors to the driving coil.

Various further and more specific objects, feature and advantages of thepresent invention will be apparent from the description given below,taken in connection with accompanying drawings illustrated by way ofexample preferred embodiments of this invention.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawings:

FIG. 1 is an electrical connection diagram of a control circuitillustrating an embodiment of the present invention;

FIG. 2 is an electrical connection diagram illustrating in detail anelectric source device which is a part of the electrical connectiondiagram shown in FIG. 1;

FIG. 3 is a diagram explaining an impulse generator and a receiver whichare used for transferring a operating signal;

FIG. 4 exhibits discharge gap means employed in the present invention;

FIG. 5 is a test circuit utilized for the discharge gap means shown inFIG. 4, and

FIG. 6 is a side view of a change-over means for an operating capacitor,which is partially sectioned.

DETAILED DESCRIPTION OF THE INVENTION -With reference now to FIG. 1,there is shown an electrical wiring diagram for a control circuitaccording to the present invention, in which a portion shown with adot-dash line E is on the ground side while a portion shown with theother dot-dash line H is on a high potential side. An electric sourcedevice P provided on the ground side is constructed as shown in FIG. 2and its output side is connected to the lowest stage of a cascadeconnection type transformer T. Thecascade connection type transformer Tconsisting of a group of transformers is enclosed in a supportingporcelain I,, and an electric power is supplied to a load L on the highpotential side through the transformer T group.

An insulation bar 18 is housed in the other supporting porcelain I andan impulse wave generator X is provided on one side of the insulationbar B, while a receiver means R adapted to convert an impulse wave intoan electrical signal is provided on the other end of said bar. (Refer toFIG. 3)

As apparent from FIG. I, in connection of a control device D and acapacitor load circuit L both being on the high potential side, acurrent transformer CT, is provided in series with the electrical sourcecircuit, a voltage produced in the secondary winding of the currenttransformer CT, is full-wave-rectified through rectifiers d, and dthereby charging a control capacitor C,,, and on the other hand thecontrol capacitor Cs is charged through a transformer T, and a rectifier(1,. There is a bidirectional two-terminal thyristor SSS connectedbetween one end of the winding of the current transformer CT, and itscenter tap, whereby, when a terminal voltage of thyristor thyristorexceeds a certain value, both terminals of the thyristor areshortcircuited thereby to suppress the terminals voltage to a certainvalue.

On the output side of a transformer T there are rectifiers d, an d andoperating capacitors C, and C, which are connected as shown in FIG. I.The connected points of the rectifiers and capacitors are furtherconnected to their respective common terminals of a change-over switchS. A series circuit of a discharge gap G and a driving coil W coupledelectromagnetically to a movable contacts of an electric power circuitbreaker (not shown) is connected between the center point of the switchS and the center tap of the transformer T0. When a discharge is effectedbetween the electrodes of the discharge gap G, and electric chargein'the capacitor C, or C is transferred to the driving coil W throughthe switch S. Then, an electromagnetic repulsion force produced betweena current produced in the coil W and a current induced in a part of themovable contact makes the latter apart from its mating stationarycontact.

In order to produce the discharge in the discharge gap G, a transformerT is provided. In addition, a silicon-controlled rectifier SCR isconnected in series to a primary winding of the transformer T and thento the control capacitor Cs, and furthermore a transformer T isconnected between the gate of the rectifier SCR and one of the terminalsof the capacitor Cs.

Referring to FIGS. 1 and 2 again, described hereinafter is a function ofthe control device according to the present invention.

Now, lets assume that the operating capacitors C, or C have beendischarged thereby completing the first breaking operation. Then, alarge current will flow to the primary winding side of the transformerT0, and to the current transformer CT,. Since said current is suppliedfrom the electric source device P placed on the ground side, thiscurrent is detected by a current transformer CT: inserted betweentransformers T, and T As a result, a control device Z is operated,thereby to actuate a contact 5 with the result that a pole of a contact4 is thrown over to a contact 4b from a contact 4311, whereby thecapacitors C, and C are quickly charged again by the whole outputvoltage of the transformer T,,. As the charge is advanced, a current ofthe current transformer CT gradually reduces. Therefore, when a value ofthe current becomes lower than a predeter mined value, the controldevice Z is restored back to its original condition thereby switchingthe contact 4, so that the capacitors are charged with a rated voltageat the contact 4a again.

A reactor Re connected in series with the current transformer CT isadapted to suppress a large current flowing when the capacitors arecharged, The reactor is relatively heavy in weight and large is size.Therefore, it is preferably provided on the electric source section onthe ground side. In other words, A space in the interior of the casingprovided on the high potential side is not so spacious, and therefore astructure such as the reactor should be provided on the ground side.

On the high potential side, the control capacitor Cs is charged throughthe transformer T, at all the times. However, as stated above, avoltage-drop due to impedance of the insulating transformer T is causedby a current flowing when the capacitor C, or C being recharged, as aresult of which an input voltage of the transformer T, is greatlylowered, whereby the capacitor Cs cannot be charged up to apredetermined value. However, when a charging current flows through thecurrent transformer CT,, the current is supplied to the capacitor Csthrough the rectifiers d, and d thereby to expedite charging thecapacitor Cs. With completion of charging the capacitor Cs, the terminalvoltage of the thyristor SSS is raised up. When this terminal voltagereaches a certain value, the thyristor SSS causes a break-down therebyto maintain the terminal voltage constant. It is desirable to employ acurrent transformer having a large exciting impedance for the currenttransformer of this circuit. An iron core such as a permalloy having ahigh permeability is preferably employed. Furthermore, it is desirablethat a voltage produced in the secondary winding is selected so that avoltage produced therein when the thyristor SSS is not connected theretobe approximately twice as much as a break-down voltage of the thyristorSSS. The break down voltage is determined from a voltage required forthe capacitor Cs.

In FIG. 3, there are shown the impulse-wave generator X and the receiverR.

When a switch 6 is turned on by a operating signal, a coil 8 is excitedby a current fed from an electric source '7. Then, a movable iron core 9is attracted towards the center portion of the solenoid coil 8, and iscollided with a great acceleration against the lower end of theinsulation bar B. It is known that a value of a compressive stress 0'can be represent by the following formula:

0' (Er/g)U,,

where:

E is a longitudinal elastic modulus of a bar,

r is a weight per unitary volume, g is a gravity acceleration, and U0 isa displacement The in slight displacement of the insulation bar atcollision. The compressive stress is propagated as a compressive wave inthe insulation bar B, and the propagation rate U is as follows:

U Er/g The propagation rates of typical insulation materials are asfollows:

Material Propagation rate (u) m/sec Glass 5,000

Resin 1,000 to 2,000

Porcelain 5,400

When the wave motion (longitudinal wave) reaches the upper end of theinsulation bar B, a piezo-electric element is imparted with acompressive force thereby to produce a high voltage. Reference symbol 11is a member having a proper mass, which is placed on the upper side ofthe piezo-electric element 10. The high voltage thus produced by thepiezo-electric element 10 is fed to the transformer T When a voltage isthus produced over the transformer T the siliconcontrolled rectifier SCRbecomes conductive whereby a current of the control capacitor Cs isdischarged out to a transformer T as a result of which a discharge iscaused between the electrodes of the discharge gap G, thereby todischarge the operating capacitor C, or C,, as mentioned previously.

As explained above, since the longitudinal wave propagating in theinsulation bar is utilized as a means of transferring the operatingsignal, according to the present invention, the signal can betransferred out with a smaller operating force at a quicker transferringrate of several thousands of meters/sec. when compared with aconventional case where a circuit breaker is driven by pull rod orpneumatically. Therefore, according to the present invention, it ispossible to obtain a operating signal transferring rate ranked next tothat in the case when light is used as a medium of transferring theoperating signal.

Referring now to FIG. 4, there is shown a construction of the dischargegap G whose essential element, namely, a capacitor is connected betweena starting electrode, or a center electrode shown in FIG. 4b, and oneside of main electrodes.

The discharge gap should start the discharge operation without actuallydelay of time and its operation is sure and stable, upon receiving of asignal. For these purposes, it is necessary to cause a great spark inthe discharge gap in response to the signal.

FIG. 5 shows an electrical connection diagram of a test circuit for thedischarge gap constructed as FIG.'4; said test circuit comprising aslidac 1, a transformer 2, a rectifier 3, and a discharging capacitor C,whose both terminals are connected to electrodes 5 and 6 of thedischarge gap G. A starting transformer 8 is connected between astarting electrode 7 and the electrode 6; while another electric source(2,, a slidac 9, a rectitier 10, a capacitor C and a thyristor GSi areconnected to a primary side of the transformer 8.

Now, after the capacitors C, and C, have been charged up to a certainvalue, respectively, a gate circuit of the thyristor GSi is activatedwith the aid of a control device (not shown). Then, as soon as a voltageis induced in a secondary winding of the transformer 8 by discharging ofthe capacitor C,,, a discharge is effected between the startingelectrode 7 and the electrode 6 and the capacitor C, is then discharged.

According to the object of the present invention, a capacitor C0 shownby a dotted line is connected between the starting electrode 7 and theelectrode 6.

The test results given on the discharge gap with the circuit thusconstructed have shown that a magnitude of a spark arc caused betweenthe electrodes 6 and 7 in the case when the capacitor C0 is connected asmentioned above is about 10 times as great as that in the case when thecapacitor C0 is not connected. Accordingly, in the latter case, thoughthe capacitor C, was discharged under conditions that a gap distancebetween electrodes 5 and 6 was set 4 mm and a charging voltage of thecapacitor C, was 4.1 kV, no discharge was effected between the mainelectrodes of the discharge gap G. On the contrary it was confirmedthrough the tests that, in the case when the capacitor C0 of 0025 [LFwas connected between the electrodes 6 and 7 according to the presentinvention, there was a discharge effected between the electrodes of thedischarge gap with the discharge of the capacitor C by application of avoltage of 2.6 kV between the electrodes 5 and 6.

When the discharge is caused between the electrodes of the discharge gapG in response to the signal, either the capacitor C, or the capacitor Cis discharged, as described with reference to FIG. 1 (in case of FIG. 1,the capacitor C, is firstly discharged). When a movable contact (notshown) is driven by the discharge thus caused, the change-over switchchanges over its contact. Therefore, when a switching signal is issued,the discharging circuit becomes ready for the discharge of the othercapacitor C The above-mentioned change-over operation will be explainedwith reference to FIG. 6, in which the same parts as in FIG. 1 aredesignated by the same symbols of numbers.

Shown in FIG. 6 is a device adapted to change-over the operatingcapacitors, which comprises the driving coil W acting as a load, theoperating capacitors C, and C,, a charging device 14 and a starting gapcontrol device 15. In this device, a starting gap 211 is provided inseries with the capacitor C, while the other starting gap 212 isprovided in series with the capacitor C,. One electrode of each of thestarting gaps 211 and 212 is fixedly supported by an insulation member20. The other electrodes 211k and 212b thereof are provided in the formof a unit with piston valves 261 and 262 and are movable in axialdirections thereof, respectively. The piston valve 261 is driven over toits starting position, as indicated, against a pressure caused by aspring 281 when a pressure P, in a tube 271 is increased. At this time,a distance between both electrodes of the starting gap 211 is 1,.Similarly, the piston valve 262 is driven to its starting position fromits open position shown in FIG. 6 against a pressure caused by a spring282 when a pressure P, in a tube 272 is increased. When the piston valve262 is at the open position as shown in FIG. 6, a distance between bothelectrodes of the starting gap 212 is l,. Therefore, even though astarting signal is applied to a starting electrode 212a, the startinggap is not activated. A tube 273 is provided between the tube 272 and achamber enclosing the spring 281 so that the pressure P, in the tube 272acts in the same direction as the spring 281 with respect to the pistonvalve 261. The tubes 2'71 and 272 are connected to a well known fluidtype flip-flop device 29. Whenever a fluid pressure as an input signalis applied to an input signal tube 291, the pressures P, and P in thetubes 271 and 272 are alternatively inversed-that is, one of thepressures is increased while the other is decreased or zeroed.

Under conditions shown in FIG. 6, the pressure P, is higher than thepressure P Furthermore, since the starting gap 211 is positioned asshown in FIG. 6, this is a state that the starting gap 211 is ready forstarting the discharge at any time whenever the operating signal isissued, while the other starting gap 2ll2 is in a state that it cannotdischarge even if the signal is issued.

Now, if the starting signal is fed to the starting electrode 211a fromthe starting gap control device 15, the starting gap 211 is discharged,whereby the operating capacitor C charged in advance is dischargedthrough the coil W. Since the discharging current flows through the coilW, a means driven by the discharging current, for instance, the contactsof the circuit breaker achieves its opening operation. When the fluidsignal is fed to the tube 291 in response to the opening operation ofthe circuit breaker, the flip-flop device 29 is operated, the pressure Pis decreased, and the pressure P is increased. Therefore, both thepressure of the spring 281 and the pressure P thus increased areimparted, in combination, to the piston valve 261, thereby to drive theelectrode 2111b to the open position apart from its mating stationaryelectrode. At the same time, the piston valve 262 and the electrode212!) formed integrally as one unit with the piston valve 262 are drivento the starting position from the open position show in FIG. 6 by theaction of the pressure P Under this condition, when a starting signal isapplied to the starting electrode 212a from the starting gap controldevice R5, the starting gap 212 and the operating capacitor C connectedin series with the former 212 are now discharged.

Furthermore, when a fluid signal is issued to the tube 291 again, thepressure P in the tube 2711 becomes higher than the pressure P in thetube 272, as a result of which the changeover device is restored back asshown in FIG. 6.

A described above, a movable provision of at least one of the electrodesof the starting gap enables the starting gap to have the function of thechangeover switch shown in FIG. I.

In the device shown in FIG. 6, when the pressure of an operating fluidis reduced, both the pressures P, and I, cannot drive the electrodes2111b and 212b, the electrodes 21 lb and 21212 are held at their openpositions by the action of the springs 281i and 282, respectively.Therefore, both the starting gaps 2lll and 212 can be made inoperativeregardless of the operation of the starting gap control device. Forinstance, in the case where a fluid pressure source is used for both thechange-over device and the circuit breaker itself and therefore thefluid pressure becomes so low that it is not proper for the circuitbreaker to conduct its opening operation, the discharging currentsupplied to the coil W is cut out thereby to avoid failures due to theoperation of the circuit breaker itself.

As obvious from the above description, the circuit breaker can beproperly controlled with the control device according to the presentinvention, in conformance with the essential objects of the circuitbreaker.

It is intended that all matters contained in the foregoing descriptionand in the drawings shall be interpreted as illustrative only not aslimitative of this invention.

We claim:

1. In a control device for a circuit breaker incorporating an insulatingtransformer and at least one capacitor and connected so that electricpower is supplied to a high potential side thereof through saidinsulating transformer to charge said capacitor, and wherein means areprovided to discharge said capacitor by an operating signal to start ahigh speed switching operation of said circuit breaker, the improvementcomprising a current limit means disposed on the ground side of saidinsulating transformer for controlling the current during recharging ofsaid capacitor.

2. A control device as set forth in claim 1, which comprises a currenttransformer means for supplying a charging current to an operatingcapacitor, and rectifier means for rectifying the output current of saidcurrent transformer means and for expediting charging of a controlcapacitor by the rectified current of said rectifier means, whereby are-closing operation is effectuated even in a recharging period of saidoperating capacitor.

3. A control device as set forth in claim 2, wherein means are providedfor recharging said operating capacitor with a voltage higher than apredetermined voltage, the voltage of the operating capacitor beingautomatically restored to a normal voltage after the voltage of theoperating capacitor reaches a predetermined charging voltage.

4. A control device as set forth in claim l, in which the means fordischarging said capacitor by an operating signal transfers an operatingsignal to a high potential side and consists of means adapted to producea stress wave signal, said operating signal being defined by said stresswave signal.

5. A control device as set forth in claim ll, wherein there is furtherprovided a device having a discharge gap disposed in the circuit of theoperating capacitor, and a capacitor having a small capacity connectedbetween one of the main electrodes and a starting electrode of saiddischarge gap.

6. A control device as set forth in claim 1, including a plurality ofsaid operating capacitors and a changeover switch means for changingover discharging circuits of said capacitors so that one of saidoperating capacitors is discharged after the other has been discharged,said change-over switch means being operated by a compressed gas incooperation with the open and close operation of the circuit breaker andbeing further controlled by a flip-flop valve means.

7. A discharge gap of a control device for a circuit breaker as setforth in claim 6, in which operation of said change-over switch isfurther effected by changing a distance between main electrodes of saiddischarge gap.

1. In a control device for a circuit breaker incorporating an insulatingtransformer and at least one capacitor and connected so that electricpower is supplied to a high potential side thereof through saidinsulating transformer to charge said capacitor, and wherein means areprovided to discharge said capacitor by an operating signal to start ahigh speed switching operation of said circuit breaker, the improvementcomprising a current limit means disposed on the ground side of saidinsulating transformer for controlling the current during recharging ofsaid capacitor.
 2. A control device as set forth in claim 1, whichcomprises a current transformer means for supplying a charging currentto an operating capacitor, and rectifier means for rectifying the outputcurrent of said current transformer means and for expediting charging ofa control capacitor by the rectified current of said rectifier means,whereby a re-closing operation is effectuated even in a rechargingperiod of said operating capacitor.
 3. A control device as set forth inclaim 2, wherein means are provided for recharging said operatingcapacitor with a voltage higher than a predetermined voltage, thevoltage of the operating capacitor being automatically restored to anormal voltage after the voltage of the operating capacitor reaches apredetermined charging voltage.
 4. A control device as set forth inclaim 1, in which the means for discharging said capacitor by anoperating signal transfers an operating signal to a high potential sideand consists of means adapted to produce a stress wave signal, saidoperating signal being defined by said stress wave signal.
 5. A controldevice as set forth in claim 1, wherein there is further provided adevice having a discharge gap disposed in the circuit of the operatingcapacitor, and a capacitor having a small capacity connected between oneof the main electrodes and a starting electrode of said discharge gap.6. A control device as set forth in claim 1, including a plurality ofsaid operating capacitors and a change-over switch means for changingover discharging circuits of said capacitors so that one of saidoperating capacitors is discharged after the other has been discharged,said change-over switch means being operated by a compressed gas Incooperation with the open and close operation of the circuit breaker andbeing further controlled by a flip-flop valve means.
 7. A discharge gapof a control device for a circuit breaker as set forth in claim 6, inwhich operation of said change-over switch is further effected bychanging a distance between main electrodes of said discharge gap.